The present invention relates, in general, to sensors, and more particularly, to a novel optical sensor.
Glass fiber optic cables have previously been used as pH sensors and to detect the presence of chemicals such as carbon dioxide, carbon monoxide, and ammonia. A small section of the cladding on a cladded fiberoptic cable is removed to expose a small section of the fiber. A sol-gel derived silica glass containing a chemically sensitive dye is prepared and applied to the outside of the exposed fiber so that light does not pass through or contact the silica glass containing the chemically sensitive dye. When exposed to different levels of the chemical analyte, the transmissive capability of the fiberoptic cable is altered thereby changing the light that passes through the cable.
One problem with the prior sensors is the manufacturing cost. A portion of the cladding must be removed in a central portion of the cable, and then the sol-gel is applied to the cylindrical cable portion that is exposed. Removing the cladding and applying the sol-gel is a labor intensive, thus, expensive operation. Additionally, it is difficult to control the thickness and uniformity of the sol-gel coating. Consequently, the response time of the sensor varies according to the thickness of the sol-gel coating. Furthermore, it is difficult to produce an array of multiple sensors suitable for sensing multiple chemicals and elements.
Accordingly, it is desirable to have an optical sensor that is easy to manufacture, that has a low manufacturing cost, that has a well controlled response time, and that can easily be formed into an array of multiple sensor elements.